This invention relates to an improved web supply and takeup system whereby the supply and take-up of the web is more precisely controlled.
An example of an Automatic Microfilm Camera using a web supply and take-up system is illustrated in U.S. Pat. No. 4,148,579 entitled Automatic Microfilm Camera by Donald J. Axelrod and John R. Flint, inventors, and assigned to the Assignee of this application.
As mentioned in the '579 patent the web or film transport mechanism transports film from a supply reel to a take-up reel, both reels being mounted on a cassette. Rollers mounted on the cassette guide the film from one reel to the other. The film is to be moved a precise amount corresponding to photographing one image per frame. A capstan and pressure roller measure out a predetermined length of film for each image photographed. Exposed film is then taken up by the take-up reel. Precisely metering out substantially identical lengths of film for each photographic image placed on the film is important so that the film can later be placed in microfilm jackets with the proper number of images per row in the jacket.
The film take-up system illustrated in the '579 patent is driven through a clutch with a predetermined torque. At times the force on the film is greater than the withholding force of the capstan and pressure roller causing additional lengths of film to be pulled through the capstan and pressure roller than is metered out. This results in a greater distance between images on the microfilm than is desired. After the film is developed it is either left in roll format or cut and inserted into microfilm jackets. If the images are not accurately and uniformily spaced, then the same number of images will not be inserted into each row in the microfilm jacket. Since a great deal of the microfilm insertion is done automatically, improper spacing of the images can result in increased down time, ruined microfilm, and over-all inefficiency.
Thus, it would be advantageous to have a system which would accurately and precisely supply and take-up a predetermined length of web or film upon demand. It would also be beneficial to build such a system easily and inexpensively and be easily adaptable to existing systems.